Wojtek does it again! Amazing, a picture for every occasion!
Note, the guy in the first pic is using a raised mask, giving a softish edge. By about 1942, the wing colour demarcation was notably softer then the previous 'hard' splinter patterns, on fighters at least. Although 'soft', many still had a definite dividing line, with just a hint of feathering, probably in the region of about 3mm or so at full scale. Therefore, a raised tape mask, if you decide to mask, would be fine, or, if you can keep it tight, go freehand, on the finest 'brush setting.